title: Agreement between indirect calorimetry and traditional tests of lactose malabsorption.
abstract: BACKGROUND
  Lactose malabsorption occurs frequently and the variable consequent intolerance may seriously impair quality of life. No reliable and convenient test method is in routine clinical practice. A recent animal study showed that the respiratory quotient changed significantly after ingestion of sucrose and lactose in naturally lactase-deficient rats.
  
  
  OBJECTIVE
  This exploratory study evaluated the relevance of monitoring the respiratory quotient after lactose ingestion to detect malabsorption.
  
  
  METHODS
  Healthy volunteers were identified and classified lactose absorbers and malabsorbers by a lactose tolerance test (25 g). After an overnight fast, a second lactose challenge was performed to monitor hydrogen excretion and respiratory quotient kinetics over 4h. Participants also completed questionnaires to score and localise their gastrointestinal symptoms.
  
  
  RESULTS
  20 subjects were enrolled (10 per group, 60% males, mean age 34 ± 4 years). Respiratory quotient kinetics were different between absorbers and malabsorbers during the first 100 min after lactose ingestion (p<0.01) and during the initial 30-50 min period. Respiratory quotient was significantly, positively correlated to peak glycaemia (R=0.74) and negatively correlated to hydrogen excretion (R=-0.51) and symptoms score (R=-0.46).
  
  
  CONCLUSIONS
  Indirect calorimetry could improve the reliability of lactose malabsorption diagnosis. Studies on larger populations are needed to confirm the validity of this test and propose a simplified measurement.
authors.affiliation: AgroParisTech, Nutrition Physiology and Ingestion Behavior, Paris, France; Vivatech, Paris, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Alexandre
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Davila
authors.forename: Michel
authors.initials: M
authors.lastname: Bouchoucha
authors.forename: Claire
authors.initials: C
authors.lastname: Bertin
authors.forename: Patrick
authors.initials: P
authors.lastname: Even
authors.forename: Christine
authors.initials: C
authors.lastname: Lamberto
authors.forename: Daniel
authors.initials: D
authors.lastname: Tomé
authors.forename: Robert
authors.initials: R
authors.lastname: Benamouzig
mesh_terms: D000328:Adult; D001944:Breath Tests; D002153:Calorimetry, Indirect; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006859:Hydrogen; D007785:Lactose / Q000378:metabolism; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000378:metabolism; D007789:Lactose Tolerance Test; D008297:Male; D015203:Reproducibility of Results; D013549:Sweetening Agents / Q000378:metabolism
chemical_list: D013549:Sweetening Agents; D006859:Hydrogen; D007785:Lactose
keywords: Lactose malabsorption; Respiratory quotient